Simply write your own custom-animation and modify the LayoutParams of your animated view.
In this example, the animation animates the height of the animated View. Of course, animating the width is also possible.

In code, create a new Animation and apply it to the RelativeLayout that you want to animate:

RelativeLayout relativeLayout = (RelativeLayout) ((LinearLayout) view.findViewById(viewId)).getParent();
// getting the layoutparams might differ in your application, it depends on the parent layout
RelativeLayout.LayoutParams lp = (RelativeLayout.LayoutParams) relativeLayout.getLayoutParams();
ResizeAnimation a = new ResizeAnimation(relativeLayout);
a.setDuration(500);
// set the starting height (the current height) and the new height that the view should have after the animation
a.setParams(lp.height, newHeight);
relativeLayout.startAnimation(a);